The joining of objects having different coefficients of thermal expansion is a problem, particularly where a secure and stable interconnection is required. For example, detectors that are used in a variety of sensors for remote sensing and imaging applications such as star trackers using a Complementary Metal Oxide Semiconductor (“CMOS”) stellar sensor or a Charged Coupled Device (“CCD”) stellar sensor to provide highly accurate attitude information or to support inertial or other navigation for a host vehicle (e.g., a spacecraft) or system often need to be precisely and securely mounted. However, the semiconductor, ceramic, or other materials associated with such detectors often have a much lower coefficient of thermal expansion than the materials making up the structure around them. The interface between the materials of different coefficients of thermal expansion is often a source of mechanical hysteresis and poses difficulties to the design and manufacturing of high-performance assemblies.
Solutions for joining objects having significantly different coefficients of thermal expansion have included the use of specialized welding techniques, adhesives, compliant interconnections, and interposer devices. However, such solutions have typically been difficult to implement, prone to allowing strain to develop in connected components, incapable of providing adequate positional stability, incapable of providing a secure connection over a wide range of temperatures, do not provide adequate levels of thermal conduction, and/or are prone to failure.
As a particular example, solutions involving welding or adhering one component to another often result in the introduction of mechanical strain in one or both of the components as a result of the differential thermal expansion of the components, which can result in alignment errors, fatigue, and failure. The introduction of an interposer can reduce such thermally induced strain. However, the use of an interposer can increase the problem of mechanical settling. The secure joining of components having differing coefficients of thermal expansion with high precision can also require high machining and alignment tolerances in order to achieve a close fit. For example, interconnections can incorporate a shrink fit plug in one component and a hole in the other component to receive the plug. However, sufficiently high tolerances are difficult to achieve, and the adequacy of completed connections can be difficult to test. Moreover, the components can separate from one another if the mechanical tolerances are improper. In addition, after the components are joined, thermal cycling may need to be performed in order to ensure that the components have fully settled and that the connection has stabilized.
Existing designs and solutions employing flexure mounting are known to provide very poor thermal conductivity through a flexure. Thermal straps can be used in combination with the mounts in order to mitigate this loss in conductivity at the expense of complexity and cost. Although such designs can be engineered to work over wide temperature ranges, they generally create more mechanical joints which increased the potential for hysteresis.